Method of increasing the strength, toughness, and ductility of manganesf steel



Patented Dec. 1, 1931 UNITED STATES PATENT. OFFICE FRANK A. FAHRENWALD, O1 CHICAGO, ILLDWOIS, ASSIGNOB 'IO AMERICAN HANG!!! STEEL COMPANY, OF CHICAGO, ILLINOIS, A. CORPORATION 01' RAIN] W01) IIGBILSING THE STRENGTH, 'rouemss, AND DUCTIIIITY 01 I0 Drawing.

My invention relates to the heat treatment of articles made of manganese steel and is based upon the discovery that certain deficiencies in the manganese steel can be over" g come by heat treating in the novel manner hereinafter described.

While manganese steel has long been noted for its toughness, shock resistance, and wear resistance it has failed to satisfactorily meet 10, certain industrial requirements because of its particularly the yield point of manganese steel by changing its composition or baddin other alloying elements thereto. one 0 these have proved successful, however, and up to the time of my resent invention it has generally been consi ered impossible to effect substantial improvements in this direction. I have discovered however, that if manganese steel be heated in an atmosphere of hydrocarbon gas without carburizing effect upon the metal of the articles, for instance in the heating step preliminary to the usual quenching operation, the resulting castings are from a fifth to a third stronger and considerably, tougher and more ductile than manganese articles heat-treated by the usual methods. In the ordinary method of heat treating manganese steel as practiced heretofore, the castings or other articles were heated in a fuel fired or electrically heated chamber to a temperature around 1,800 F. (or around 980 C.) and maintained at that temperature for a sufiicient time to insure uniformity and then quenched in water.

Instead of heating manganese steel as reviously in the ordinary products of com ustion or in the oxidizing atmosphere of the electric furnace, my process subjects manganese steel articles to radiant heat in a spa cious chamber containing free, unoxidized hydrocarbon gas; the chamber being heated preferably, either externally by fuel-firing or internally by means of electrical resistance elements mounted within the chamber. The manganese steel articles so treated, when subsequently quenched, possess charactermama ma mm as, am. mm It. mu.

istics never heretofore found in manganese steel castings processed by any other method.

In the case of small cast manganese steel chain, for instance, treated by this process,

the breaking strength is approximately 17,000

pounds, whereas the same chain treated by previous methods would only sustain 13,000 pounds, and in the case of test bars heattreated before machining to standard dimensions,the difference between gas treated and ordinary treated castings, determined 'for me by a reputable commercial testing establishment and which is typical of'the relative value of the new manganese steel as against manganese steel produced by the old standard- .5

method, is represented by the following figures:

Physical properties of manganese steel i I make no attempt to explain the chemical or other reactions which may combine to produce this remarkable improvement, and simm ply claim the process and the products as such. In my' new process practically any low sulphur hydrocarbon gas, such as natural or artificial illuminating or va rs of alcohol, or as oline, or v0 atile distillation products 0% coal may be em load; and the treatment temperature shou (1 above about 1650 F. or above 900 C.

As a typical procedure and the best way now known to me of carrying out the invention, introduce the manganese steel castings, unboxed and fully exposed, into the heatin chamber of an electric resistance furnace, an at or before the time that the castin begin to show color, introduce ordinary ill u minating gas into the same chamber with freedom of convection and in quantity sufiicient to quickly consume the oxygen in the chamber and cause the atmosphere to assume a smoky reducing condition. Continue or repeat the 58- ment containin introduction of the gas in a small ter of atmosphere to the end of the heating ste and until the discharge door is about 5 to he opened and the castings raked out.

This process is not to be confused with the process of case hardening ordinary types of steels, wherein onl the surface and not the interior or the stee is made to absorb carbon, and where the abso tion of carbon is of such a high degree that w en quenched after heating, an extremely hard surface is produced. In my process for the treatment of manganese steel in an atmosphere containing carbon metals 0 the articles and of the surface of the articles, in fact, the surface is somewhat softer than results from treatment by ordinary means, as practiced heretofore; and the effects of the hydrocarbon environment occur flow or bon gas, and thereby quantity sufiicient to maintain this characste free hydroas, there is no carbunizing of the completing the heating without carburizing the metal of the artic es.

Si 6th ay of March 1928.

- FRANK a 'FAHRENWALD.

while the metal is at temperature a propriate for quenching, and are followed y uenching, which circumstances may have t air in-- fluence upon the surprising results obtained from the procedure.

I claim:

1. The recess of heat treating manganese steel artic es, which comprises the steps of subjecting said articles to a temperature t above about 1650 F. (above about 900 Ci) and maintaining around said articles, at least a while they are at such temperature, a noncarburizing, environment containin carbon gas and without carburizmg t ticles.

hydro- 0 metal of the articles, and then quenching said ar- 2. The improvement in the art of heattreating manganese steel articles, which consists in carrying out the critical portion of the heating step which is preliminary to bon containin reducing. atmo here but without carburizing the metal of t e articles,

' 4i and by subjection to a heat source which is independent of said atmosphere, and then q quenching the articles.

'8. The improvement in the art of heat treating articles of manganese steel, which consists in bringing such articles up to the quenchin temperature of said treatment and, at least w ile the articles are at said temper ature, exposing them directly to a substantially unigm'ted, non-carburiz' environwithout carburizmg the metal of the artic es, and then quenchin the articles. Y

4. In the art of eat treatment of articles of manganese steel, the improvement which 00 consists in maintaining around the articles e5 rizing atmosphere containing free hydrocara readily oxidizablie as.

quenching, while the manganese steel articles are exposed to a freely convective hydrocared at Chicago Heights, Illinois, this 7 claim 1cm: or connection 7 Patent No. 1,834,206. Granted December 1, 1931, to

FRANK A. FAHRENWALD.

It is hereby certified that error appears in the printed specification of" the above numbered patent requiring correction as follows: Page 2, line 16, after "and" insert no hardening; and that the said Letters Patent should be read with this correction therein that the same may conform to the record ofthe caae in the Patent Office. 1

Signed and sealed this 16th day of February, A. D 1932.

M.J.'Moore, (Seal) Acting Commissioner of Patente. 

